This invention relates generally to bags of the gusseted, square-bottomed type and a method of making the same.
Gusseted, square-bottomed bags are disclosed in U.S. Pat. No. 2,496,796; 3,017,069 3,342,402; and 4,490,131. As disclosed in these patents, the bags of this type generally comprise an outer sheet of paper and an inner liner of an impervious heat sealable material such as a plastic (synthetic resin). The bag is made of a tube and the bottom end of the bag is formed by making a diamond fold comprising a triangular fold portion and a partly rectangular tab fold portion. After the triangular fold portion and the tab fold portion are sealed, the bottom of the bag is completed by folding over the tab fold portion onto a previously folded over triangular fold portion. The tab fold portion is caused to adhere to the bottom of the bag by applying suitable adhesive between the contiguous faces of the tab fold portion and the triangular portion of the bag bottom structure.
In accordance with the present invention there is provided a bag and a method of makingm, the same which provides an improved bottom construction which is very effectively sealed so that the bag can contain many materials, including liquids, without any seepage through the bag bottom. To this end, the bag is made by a method wherein a special seal is applied at a location at the intersection between the fin seal and the cross seal. This additional seal has been found to improve the sealing of the bag bottom structure such that the bag can be used in many applications which heretofore bags of the indicated type were unacceptable. For example, in the microwave cooking of food products, the bags are required to contain liquids, such as water, oil, etc., during storage and during the cooking processes wherein such liquids become very hot. In these applications, even the slightest pin hole or other opening in the seal of the bag bottom would cause a leakage or staining problem. Bags made by the method of the invention comprising the special seal at the intersection of the fin seal and cross seal have overcome these problems.